Process for recovering aldehydes and ketones



Patented Mar. 6, 1951 PROCESS FOR RECOVEBING ALDEHYDES AND KETONES Vesta F. Michael,

lind i] and Gas Company, notation of Delaware Tulsa, Okla., ssslgnor to Stancmoms:-

No Drawing. Application July 18, 1947, Serial No. 762,001

Claims. (Cl. 206-586) This invention relates to the recovery or aldehydes and ketones from solutions thereof. More particularly, it relates to an improved process for separating aldehydes and ketones from aqueous solutions oi blsulflte-aldehyde and bisulflteketone adducts.

It is well known that alkali-metal bisulfltes iorm addition compounds with aldehydes and with ketones. and this reaction has been used as a means for separating aldehydes and ketones from other organic materials and for isolating the aldehydes or ketones in substantially pure form. In carrying out such a purification procedure, the aldehyde or ketone is first extracted with a blsulflte solution, suitably sodium bisulflte, which ordinarily has a pH between about 3 and 5 when prepared by dissolving sodium bisulflte in water. The aqueous extract is then made strongly acid or strongly alkaline, the bisulflte salt being thereby destroyed. and the aldehyde or ketone is released. ordinarily as a separate liquid phase. Alternatively, the aldehyde and/or ketone may be released from the extract by heating to an elevated temperature, without adjustment of the pH. As a further alternative, the aldehyde and/or ketone may be separated from the extract, without adjustment of the pH, by extraction with a suitable solvent, the adducts being thereby progressively displaced toward the free aldehyde and/or ketone, owing to the equilibrla that are known to exist.

I have now discovered that the separation of aldehydes and/or ketones from aqueous solutions oi bisulflte adducts is greatly facilitated by carrying out the heat treatment and/or extraction of the aqueous adduct solution at a pH within the range of about 6 to 7: and I have obtained improved results, compared with the results obtained in the prior art, by carrying out the separation within the range of about pH 5 to 8.

My process may embody a preliminary extraction step, wherein aldehydes and/or ketones are removed from other organic liquids by extraction with an aqueous solution of a water-soluble blsulflte. The preliminary extraction is preferably carried out at ordinary temperatures, but may be carried out at temperatures as low as around 0' C. The extraction of ketones may be carried out as high as around 40 0., and the extraction of aldehydes proceeds satisfactorily at temperatures as high as 80 c.

Ketones may be regenerated from the resulting extract by heating to a temperature above about 40' 0.. and aldehydes may be regenerated by heating to temperatures above about C. The regeneration is preferably carried out by steam distillation at or above the temperatures designated above. The separation of aldehyde! and/or ketones may also be carried out by extraction with a suitable solvent, such as a light hydrocarbon fraction, an alkyl ether, or an ester, at ordinary or elevated temperatures.

In addition to a striking improvement in the efllciency of regenerating aldehydes and ketones, my process has other notable advantages: In the pH range that I prefer to use. the problem of apparatus corrosion is virtually eliminated. Moreover, the losses of active material from the system are small. Sulfur dioxide is not liberated during heat treatment or distillation; there is substantially no loss in bisulflte concentration of the extracting solution through reduction by i'crric ions or through other mechanisms: and there is substantially no tendency to precipitate bisuliite adducts in the cold section of the apparatus after repeated cycles. My process is therefore ideally adapted to operation on a continuous or semicontinuous basis, with recycling of reenerated bisulnte solution.

Water-soluble bisuliltes in general are suitable for carrying out my process, including bisuifltes of alkali metals. specifically lithium, sodium, potassium, rubidium, and cesium: alkaline-earth metals, such as calcium, barium, and strontium: and ammonium and substituted ammonium, such as methylammonium. diethylammonium, tris- (2'- hydrox'yethyl) ammonium, benzyltrimethylammonium, and the like. I prefer, however, to use sodium and/or potassium bisulfltes, owing to their cheapness and availability. Solutions having a concentration between about 1 and 10% by weight, calculated as the anhydrous bisulflte salt. are most satisfactory. For most eflective extraction of aldehydes or ketones from any given solution, the solution should be contacted with substantiaily more than the equimolar ratio or bisulflte, based on the number of carbonyl groups present, and the extraction is preferably carried out in countercurrent flow.

My process is suitable for recovering or isolating aldehydes and ketones from solution in virtum ally any organic liquid which is not miscible with aqueous bisulflte solutions and which does not react with or destroy the blsulflte. As examples of such organic liquids may be cited alcohols such as n-butyl alcohol, capryl alcohol, benzyl alcohol, cyclohexanol, and furfuryl alcohol; aliphatic hydrocarbons, such as hexanes, heptanes, octanes. petroleum naphthas, and the like; alicyclic hydrocarbons. such as cyclohexane, methylcyclohexane. and the like; aromatic hydrocarbons, such as benzene. toluene. xylene, and the like; and ethers, such as ethyl ether. isopropyl ether, butyl ether. ethyl butyl ether, and the like.

From such liquids, my process may be used to separate aldehydes, such as acetaidehyde, propionaldehyde, butyraldehyde, isobutyraldehyde, valeraidehyde, octanal, benzaldehyde, furfural. and the like; and ketones. such as acetone, ethyl methyl ketone, methyl n-propyl ketone, methyl n-butyl ketone, cyclopentanone, cyclohexanone, and the like. V

My invention is particularly suited for the separation of ketones from hydrocarbon solutions thereof produced in the hydrogenation of carbon monoxide by the Flscher-Tropsch process, and by the numerous modifications thereof; for the recovery of aldehydes and ketones from the alcohols produced by the so-called Synol" process; for the recovery of aldehydes and ketones from solution in organic liquids resulting from the oxidation of hydrocarbons; and for the recovery of aldehydes from the hydrocarbon solutions thereof resulting from the contacting of oleflns with carbon monoxide and hydrogen in the socalled "x0" process.

The following examples will more clearly illustrate my invention and demonstrate its superiority over the prior art processes:

Example I The following example shows that the extraction of carbonyl compounds in my process takes place very rapidly. effective equilibrium being attained in a contact time as short as one-half minute.

An aqueous sodium bisulnte solution was prepared by dissolving 260 grams of sodium metabisulfite (NasSzOs) and 17.4 grams of sodium hydroxide in water and diluting to one liter. The sodium hydroxide reacted with part of the sodium bisulfite to form sodium sulfite, and thereby raised the pH of the solution to 6.6 from an initial value of 4.2. A sufficient quantity of sodium bisulilte was present over the amount required to react with the sodium hydroxide to form a solution containing 6.8 percent by weight of free sodium bisulfite.

A series of extractions were made at 25 C. at contact times between 0.5 and minutes. using in each experiment one liter of bisulflte extractant solution, prepared as described above, to extract one liter of a hydrocarbon solution containing 0.328 gram-mole of mixed aldehydes and ketones, comprising primarily C2-C1: compounds. The results were as follows:

Example 11 The following example illustrates the extraction of a typical aldehyde from solution in a hydrocarbon and the subsequent regeneration of the aldehyde according to my process.

A '180-ml. portion of sodium bisuliite solution. prepared as described in Example I, was agitated with one liter of heptane containing 5 percent butyraldehyde by volume. Within three minutes. the temperature of the reacting mixture increased from 26 to 34 C., after which the temperature slowly decreased. The aqueous extract was separated from the heptane and steam distilled. The results were as follows:

Butyraldehyde in heptane, vol. percent:

Before extraction 5 After extraction 0.002

pH of bisulflte solution:

Before extraction 8.62 After extraction 7.93 After distillation 6.68 Butyraldehyde recovery, percent of original:

First ml. condensate 36.4 Second 100 ml 20.4 Third 100 ml 12.0

Total 68.8

1 Volume adjusted to original by addition oi distilled water.

Example 11! The efl'ect of pH on the recovery of butyraldehyde from sodium bisulilte solutions by steam distillation was studied by preparing four solutions of aqueous 2.5% sodium bisuifite having a range oi pH levels from 4.21 to 6.53. A 'i80-ml. portion of each solution was then reacted with 25 ml. of butyraldehyde, and the adduct solution was steam The following example demonstrates that the bisuliite extractant solutions of my invention may be effectively regenerated by steam distillation, and when so regenerated, are as effective as fresh bisulilte extractant solution. Both the bisulilte solptions and the hydrocarbon solutions of carbonyl compounds were substantially the same as those employed in Example I.

In the experiment with fresh bisulflte solution. a single one-liter portion of the hydrocarbon solution of carbonyl compounds was extracted repeatedly with fresh one-liter portions of bisuliite solution. and the hydrocarbon solution was analyzed for carbonyl compounds after each extraction.

In the experiment with regenerated bisulflte solution, the regenerated bisulflte solution was first prepared by using a one-liter portion of fresh bisulflte solution for nine extraction and stripping cycles on successive one-liter portions of the hydrocarbon solution of carbonyl compounds. Then a single one-liter portion oi the hydrocarbon solution of carbonyl compounds was extracted repeatedly with the regenerated bisulfite solution, the aqueous extract being substantially freed from carbonyl compounds by steam distillation after each extraction, and the hydrocarbon ratiinate being analyzed for carbonyl compounds.

The cumulative results are given in the following table:

Carbonyl Oompounds Extracted, Cumulative Extraction No.

Recycled Extractant. mole per cent Fresh Extractant. mole per cent mean $3. chosen Example V The following example demonstrates the feasibility oi recycling the bisuliite solutions employed in my invention. A single one-liter portion of pH 6.6 sodium bisulfite solution was used successively to extract ten one-liter portions of a hydrocarbon solution containing carbonyl compounds. Both solutions were identical with those used in Example 1. After each extraction, carbonyl compounds were removed from the bisulflte solution by steam distillation at 100 C. The results are given in the following table:

At the conclusion of the ten extraction and stripping cycles, the residual aldehydes and ketones in a portion of the steam-stripped bisulflte extractant solution were liberated with sodium carbonate, and aldehydes and ketones equal to 1.6 volume percent of the extractant solution were recovered. This very low quantity of recycled carbonyl compounds, after ten cycles, together with the maintenance of extraction etliciency, indicates that the solution could be used for many more cycles before becoming inefiective.

While the foregoing examples illustrate the preferred forms of my invention, it will be understood that departures may be made therefrom within the scope of the specification and claims. In general, it may be said that any modifications or equivalents that would ordinarily occur to those skilled in the art are to be considered as lying within the scope of my invention.

In accordance with the foregoing specification, I claim as my invention:

1. In a process for the recovery of a carbonyl compound selected from the group consisting of aldehydes and ketones from a mixture comprised thereof, the steps which comprise adjusting the pH of an aqueous solution of a water soluble bisuliite to a value between about 5 and 8, said solution consistin essentially of a mixture of suldie and bisulilte ions, thereafter mixing said aqueous solution with said mixture containing said carbonyl compound to form the corresponding bisulflte adduct of said carbonyl compound, and heating the resulting mixture to a temperature above the decomposition temperature of said adduct without the addition of alkali to said mixture subsequent to the formation of said bisulfite adduct.

2. The process of claim 1 in which the pH 01' said aqueous bisulflte solution ranges from about 6 to about 7.

3. In a processdcr the recovery of a carbonyl compound selected from the group consisting of aldehydes and ketones from a mixture comprised thereof, the steps which comprise adjusting the pH 01' an aqueous solution of a water soluble bisulfite to a value between about 5 and 8, said solution consisting essentially of a mixture oi sulflte and bisulfite ions, thereafter mixing said aqueous solution with said mixture containing said carbonyl compound to form the corresponding bisulflte adduct 01' said carbonyl compound, and steam distilling the resulting mixture to a temperature above the decomposition temperature of said adduct without the addition of alkali to said mixture subsequent to the formation of said bisulflte adduct.

4. In a process for separating and recovering a carbonyl compound selected irom the group consisting of aldehydes and ketones from a liquid hydrocarbon solution thereof, the steps which comprise adjusting the pH of an aqueous solution of a water soluble bisulfite to a value between about 5 and 8, said aqueous solution consisting essentially or a mixture of sulflte and b'suliite ions, thereafter mixing said aqueous solution with the liquid hydrocarbon solution of said carbonyl compound to form the corresponding bisulflte adduct or said carbonyl compound, and heating the resulting mixture to a temperature above the decomposition temperature of said adduct without the addition of alkali to said mixture subsequent to the formation of said bisulilte adduct.

5. In a process for separating and recovering a carbonyl compound selected from the group consisting of aliphatic aldehydes and aliphatic ketones from a liquid hydrocarbon solution thereof, the steps which comprise adjusting the pH oi an aqueous solution of a water soluble bisulfite to a value between about 5 and 8, said solution consisting essentially of a mixture of suliite and bisulfite ions and containing between about 1 and 10 weight per cent oi an alkali metal bisulflte, thereafter mixing said aqueous solution with said liquid hydrocarbon solution to form the corresponding bisuliite adduct of said carbonyl compound, stratifying and withdrawing an aqueous extract containing a bisultlte adduct of said carbonyl compound, heating said aqueous extract at a pH between about 5 and 8 and at a temperature above the decomposition temperature of said bisuliite adduct without the addition to alkali to said adduct subsequent to the formation oi said bisulfite adduct, withdrawing said carbonyl compound in purified form as a distillate fraction and regenerated aqueous bisulflte solution as a bottoms fraction, and recycling said regenerated aqueous bisulflte solution for the extraction of an additional quantity of said liquid hydrocarbon solution.

VESTA F. MICHAEL.

(References on following M) 8 REFERENCES CITED OTHER REFERENCES The following references are of record in the Fieser et 0.1.. rganic Chemistry, Heath and 00., (1944) pages 206-209.

tile of this patent:

Stewart et 111., American Chemical Society UNITED STATES PATENTS 5 Journal. v01. 54, (1932) pages 3555-3569. Number Name Date Stewart et al., Amer. Chem. Soc. Jumu, vol. 54,

698,355 Bazlen 1902 (1032) pages 23334340.

FOREIGN PATENTS Number Country Date 10 267,991 Great Britain June 9, 1927 

1. IN A PROCESS FOR THE RECOVERY OF A CARBONYL COMPOUND SELECTED FROM THE GROUP CONSISTING OF ALDEHYDES AND KETONES FROM A MIXTURE COMPRISED THEREOF, THE STEPS WHICH COMPRISE ADJUSTING THE PH OF AN AQUEOUS SOLUTION OF A WATER SOLUBLE BISULFITE TO A VALUE BETWEEN ABOUT 5 AND 8, SAID SOLUTION CONSISTING ESSENTIALLY OF A MIXTURE OF SULFITE AND BISULFITE IONS, THEREAFTER MIXING SAID AQUEOUS SOLUTION WITH SAID MIXTURE CONTAINING SAID CARBONYL COMPOUND TO FORM THE CORRESPONDING BISULFITE ADDUCT OF SAID CARBONYL COMPOUND, AND HEATING THE RESULTING MIXTURE TO A TEMPERATURE ABOVE THE DECOMPOSITION TEMPERATURE OF SAID ADDUCT WITHOUT THE ADDITION OF ALKALI TO SAID MIXTURE SUBSEQUENT TO THE FORMATION OF SAID BISULFITE ADDUCT. 